Definitely the Everybody's Nintendo Channel with some demos right off the bat.

Also wouldn't mind an update to the Everybody Votes Channel. That channel is so pointless right now. It could be used by publishers to get feedback from gamers and what they want on upcoming games. Instead its used to ask pointless questions that nobody cares about, I haven't touched that channel since it came out.

A music channel would be useful too. I'm not asking much from the hardware, just a channel that will act as a player to listen to music off your SD Card. I know the photo channel can do it too but clicking each song you want is stupid plus if you click "all mp3 files" it just plays everything and you have no control. Some sort of player would be nice.